I'm pretty sure it is for showing your own work, but I wouldn't worry about it. The "Show" label is relatively minor, and this is certainly an interesting project to share!

There's a link to the rules/guidelines at the top of the "show" page:

https://news.ycombinator.com/showhn.html

> Show HN is for something you've made that other people can play with. HN users can try it out, give you feedback, and ask questions in the thread.